Comparative study of dma content and interphase nucleolar organizer regions in human pituitary adenomas

DNA content and the number of nucleolar organizer regions (NORs) are claimed to be valuable markers of biological behavior in many tumors. Forty-three human pituitary adenomas removed by surgery were embedded in paraffin and studied by flow cytometry in order to establish DNA index and percentage of cells in different phases of cell cycle. In 31 of these tumors, silver staining showing argyrophilic proteins bound to NORs (AgNORs) was applied. DNA analysis revealed DNA aneuploidy in 32% of the adenomas. The highest number of aneuploid tumors was found in silent corticotroph adenomas (5 of 9), followed by prolactin cell adenomas (3 of 6). The lowest number of aneuploid tumors was noted in null cell adenomas and oncocytomas. The presence of an aneuploid peak could not be correlated with the size of adenomas or with invasiveness. The number of cases with S fraction higher than median was not increased in large or invasive tumors. No close correlation was found between DNA index and AgNOR reading or between S fraction and AgNOR number. These results show that DNA index and AgNOR counting must be interpreted with caution as proliferation markers in pituitary adenomas.